Sunday NFL pregame shows are known for their hearty laughter. But there has been little to guffaw about this season.

The NFL's TV numbers slide has infected long-running pregame shows on ESPN, NBC Sports and CBS Sports. The hardest hit has been ESPN's "Sunday NFL Countdown" (10 a.m. to 1 p.m. ET), which has lost 15 percent of its viewership.

With Samantha Ponder succeeding Chris Berman as host after 31 years, ESPN's "Countdown" has averaged 1.138 million viewers through the first nine weeks of the 2017 season. That's down 14.8 percent from 1.299 million viewers for the same time period in 2016 and down a whopping 25.4 percent from 1.525 million viewers during the same stretch in 2015.

NBC's "Football Night in America," the most-watched studio show in all of sports, averaged 7.359 million viewers through the first nine weeks of the 2017 season. That's down 7.2 percent from the same period last season. CBS' "The NFL Today" averaged 3.3 million viewers over the first nine weeks of the season, down 5.7 percent from the same stretch last year. Bolstered by its bigger NFC TV markets, "Fox NFL Sunday," which has been the top Sunday morning pregame show for decades, is the only NFL pregame show that remains virtually flat this season, with average viewers ticking up 0.6 percent to 4.705 million.

Of all the NFL pregame shows, ESPN's "Countdown" made the most sweeping changes during the offseason. Many insiders were surprised when the 31-year-old Ponder jumped from "College GameDay" into the "Countdown" host chair over Trey Wingo and/or Suzy Kolber, who were more experienced. Tom Jackson, Berman's venerable "Countdown" partner, retired two years ago. ESPN hired TV rookie Rex Ryan to join returning cast members Randy Moss, Charles Woodson and Matt Hasselbeck.

Samantha Ponder (Getty Images)

ESPN's new "Countdown" producers Matthew Garrett and Chad Minutillo revamped everything from the set to the show's opening sequence to the graphics. Instead of personalities gathering around a traditional TV desk, the show has a more open feel, with Ponder and Co. sitting on couches facing each other; hand-held cameras moving fluidly between the cast and NFL insiders Adam Schefter, Chris Mortensen and Louis Riddick. ESPN also extended the show to three hours from two hours.

TV insiders point to multiple reasons for the downturn of "Countdown." TV viewing is down across the board, and sports are not immune. Some old-school viewers clearly miss the gravitas of Berman, Jackson and other former cast members. With Hurricane Irma ravaging the Southeast in Week 1, opening week ratings for "Countdown" dropped 33 percent. The show has gained back ground but remains in a big hole. Many fans still seem turned off by NFL player protests during the national anthem as well as the apparent blackballing of quarterback Colin Kaepernick. President Donald Trump also has urged his followers to boycott the NFL until the league forces players to stand during the anthem.

Despite those issues, Seth Markman, ESPN coordinating producer, gave the "Countdown" cast and crew a strong vote of confidence.

"We are thrilled with 'Countdown' this season, both in front of the camera and behind the scenes," Markman said in a statement to Sporting News. "Sam and Rex, our newcomers, developed an instant chemistry with Randy, Charles, Matt and the other members of the team. The show is much more conversational this year, which was one of our goals, and we continue to cover the entire NFL every week with expert analysis, terrific features and our well-connected reporters in the field."

It's good that Markman and the top brass in Bristol is giving "Countdown" room to let a new show chemistry develop. But sources say the show's TV numbers are causing concern at ESPN's corporate campus. There has been more far more discussion about "Countdown" than there has been about Ponder putting the kibosh on ESPN's short-lived partnership with Barstool Sports.

"This is what people are talking about in Bristol. What's happening with 'Countdown,'" a source said. "Not the Barstool deal. That was small potatoes."

ESPN's competitors smell blood. Fox Sports boss Eric Shanks told SN in September he sees an opening for Charissa Thompson's three-year-old "Fox NFL Kickoff" to beat "Countdown" as the top NFL pregame show in the 11 a.m. to 12 noon ET slot this year.

ESPN is still loaded with talent in front of and behind the camera, and there are plenty of moves the network can make to improve "Countdown." ESPN could give more air time to NFL insiders like Josina Anderson and Sal Paolantonio, who break news on Sundays. The show comes alive when these news-breakers provide something fresh to analyze rather than rehashing old news.

Younger cast members like Hasselbeck, Moss and Woodson should remember ESPN hired them because they're relatively fresh off the playing field, and they know today's game and players — not because the network wants them to shout and jump around like teenagers.

Times have changed for the NFL and its TV partners. This has been the most troubled, challenging and controversial season in decades, and viewers are abandoning the league.

All the NFL pregame shows should consider this a wake-up call. It's time for ESPN's revamped "Countdown," specifically, to take the game — and themselves — more seriously.